[lldb-dev] Is DBGSearchPaths supported for configuring dSYM lookups?

[Ivan Hernandez via lldb-dev]

Thank you for the very detailed explanation Greg! Good to know about why
DBGSpotlightPaths was not working and that DBGSearchPaths is a possible
option. I do expect this directory will get quite large so it looks like
DBGFileMappedPaths is the better alternative.

On Wed, Feb 17, 2021 at 6:53 PM Greg Clayton <clayborg at gmail.com> wrote:

> DBGSpotlightPaths is to limit spotlight searches to _only_ those
> directories, but they must be valid locations that spotlight would normally
> index. If you want to see if spotlight indexes a directory that contains a
> dSYM file, then you can us "mdls":
>
> $ mdls a.out.dSYM
> _kMDItemDisplayNameWithExtensions      = "a.out.dSYM"
> com_apple_xcode_dsym_paths             = (
>     "Contents/Resources/DWARF/a.out"
> )
> com_apple_xcode_dsym_uuids             = (
>     "4B8A7479-4DF6-3828-AB99-3EF71E79B00E"
> )
>
>
> if you see "com_apple_xcode_dsym_paths" and "com_apple_xcode_dsym_uuids",
> then spotlight already indexes this directory and nothing should need to be
> done. This won't work for locations that spotlight normally doesn't index
> like "/tmp/*", "~/Library/Caches/*" and many more locations. This will just
> let you know if spotlight is indexing files already.
>
> If you have a directory that contains dSYM files that you want to search,
> you have a few options:
> 1 - specify a directory that will be used for the current LLDB session only
> 2 - add dsym files manually as you need them
> 3 - specify a directory that will always be searched for all debug sessions
>
> For solution #1 you can do this in LLDB with a setting:
>
> (lldb) settings set target.debug-file-search-paths /symbols/dir/number1
> [/symbols/dir/number2 ...]
> (lldb) target create ....
>
> Any dSYM files that aren't found by spotlight, will fall back and look for
> matching dsym files in the directories you specify for the current LLDB
> session only.
>
> For solution #2, you can add dSYM files manually:
>
> (lldb) target create a.out
> (lldb) target symbols add /path/to/libfoo.dSYM
>
> LLDB will find the executable that matches /path/to/libfoo.dSYM and add it
>
> For solution #3, you can modify the DebugSymbols.framework global defaults
> which will help LLDB and any other Xcode tools (sample, Instruments, Xcode,
> etc) to find your symbols:
>
> $ defaults write com.apple.DebugSymbols DBGSearchPaths -string
> /single/path/to/search
> $ defaults write com.apple.DebugSymbols DBGSearchPaths -array
> /path/to/search1 /path/to/search2
>
> The main issue with this settings, is each time you have a program that
> loads DebugSymbols.framework (like LLDB), it will need to scan this entire
> directory and find all matching dSYM files. If you end up placing a lot of
> files in this directory, then it can become a performance cost. So this
> method is not preferred due to its possible costs that depends on how many
> dSYM files are in these directories.
>
>
> A better solution that works well for solution #3 but has no cost
> associated with it is to store you dSYM files in a directory that isn't
> indexed by spotlight, then have a script that ends up chopping up your UUID
> into 4 byte hex values as specified in File Mapped UUID Directories
> <https://lldb.llvm.org/use/symbols.html#id3> page. This allows direct
> access for looking up symbol files when needed and doesn't cost you much
> besides a few stat() calls when you are looking for specific symbols.
>
> More comments inlined below!
>
>
>
>
> On Feb 11, 2021, at 8:29 AM, Ivan Hernandez via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
>
> Hello,
>
> I am in need of configuring dSYM lookups on macOS for a directory under
> ~/Library/Caches which is not indexed by Spotlight and does not seem to be
> picked up when adding my directory to DBGSpotlightPaths.
>
>
> Spotlight purposely doesn't index in ~/Library/Caches at all and
> DBGSpotlightPaths setting for DebubSymbols.framework is used to only limit
> spotlight's search to existing directories. The DBGSpotlightPaths setting
> is typically used when you might have multiple external drives and you want
> to limit spotlight searches to only a few root drives that contain symbols.
> It won't cause a location that isn't indexed by Spotlight to suddenly
> become indexed.
>
> The Symbols on macOS <https://lldb.llvm.org/use/symbols.html> page
> includes "Explicit search paths" as a method of dSYM lookups but mentions
> no way of configuring it. I happened to come across this very old GDB
> release notes
> <https://opensource.apple.com/source/gdb/gdb-696/doc/ReleaseNotes.xml>
> page which mentions that DBGSearchPaths can be used to configure explicit
> search paths.
>
>
> Yes this is correct as I detailed above, but it comes with unacceptable
> costs according to most people as each process has to scan these
> directories recursively, so you want to make sure to specify a directory
> with only a few files if you do end up using this method. If you specify an
> entire hard drive, each time you start a process that uses
> DebugSymbols.framework, it will recursively search the entire drive and all
> subdirectories for dSYM files which can obviously slow things down!
>
>
> I can use DBGFileMappedPaths or DBGShellCommands but DBGSearchPaths seems
> to be working fine and looks like a much simpler approach if it is intended
> to be supported in the long term.
>
>
> It has been support for over 10 years, so yes, this is supported and will
> continue to be, as long as you know the costs involved and are ok with
> that, you can use this method.
>
> Greg Clayton
>
>
> Thanks,
> Ivan
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